The person heart is a four-chambered muscular organ, shaped and sized about like a man"s closeup of the door fist with two-thirds of the mass to the left that midline.

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The heart is attached in a pericardial sac that is lined with the parietal class of a serous membrane. The visceral class of the serous membrane creates the epicardium.

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Layers of the heart Wall

Three class of tissue kind the heart wall. The external layer that the heart wall is the epicardium, the center layer is the myocardium, and also the inner great is the endocardium.

Chambers of the Heart

The interior cavity of the heart is split into four chambers:

Right atriumRight ventricleLeft atriumLeft ventricle

The 2 atria are thin-walled chambers that receive blood from the veins. The two ventricles room thick-walled chambers the forcefully pump blood the end of the heart. Differences in thickness that the heart chamber wall surfaces are as result of variations in the amount of myocardium present, which reflects the amount of pressure each chamber is required to generate.

The ideal atrium obtain deoxygenated blood native systemic veins; the left atrium receive oxygenated blood from the pulmonary veins.

Valves of the Heart

Pumps need a collection of valves to save the liquid flowing in one direction and also the heart is no exception. The heart has two species of valves that store the blood flowing in the correct direction. The valves between the atria and ventricles are called atrioventricular valves (also called cuspid valves), if those in ~ the bases of the large vessels leave the ventricles are referred to as semilunar valves.

The right atrioventricular valve is the tricuspid valve. The left atrioventricular valve is the bicuspid, or mitral, valve. The valve between the ideal ventricle and pulmonary trunk is the pulmonary semilunar valve. The valve between the left ventricle and the aorta is the aortic semilunar valve.

When the ventricles contract, atrioventricular valves nearby to avoid blood native flowing earlier into the atria. When the ventricles relax, semilunar valves close to prevent blood native flowing back into the ventricles.

Pathway of Blood through the Heart

While that is convenient to define the flow of blood through the best side of the heart and also then with the left side, it is vital to realize the both atria and ventricles contract at the exact same time. The heart functions as 2 pumps, one top top the right and also one ~ above the left, working simultaneously. Blood flows from the right atrium to the best ventricle, and then is pumped to the lungs to receive oxygen. From the lungs, the blood flows to the left atrium, then to the left ventricle. From over there it is pumped to the systemic circulation.

Blood supply to the Myocardium

The myocardium the the heart wall is a functioning muscle that needs a continuous supply that oxygen and nutrients to function efficiently. Because that this reason, cardiac muscle has an extensive network of blood vessels to carry oxygen to the contracting cells and to remove waste products.

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The right and also left coronary arteries, branches the the ascending aorta, it is provided blood come the wall surfaces of the myocardium. ~ blood passes through the capillaries in the myocardium, the enters a mechanism of cardiac (coronary) veins. Most of the cardiac veins drainpipe into the coronary sinus, which opens right into the best atrium.